The present invention relates to an improved disposable delivery system for intraosseously delivering anesthesia to the jawbone or other parts of the living body. In particular, the present invention relates to an improvement of the disposable intraosseous anesthesia delivery apparatus and method disclosed in earlier U.S. application Ser. No. 09/165,010 and earlier PCT Application U.S. Ser. No. 99/07728, the entire contents of both of which are incorporated herein by reference.
The present invention is described in detail below with respect to application of dental anesthesia, but the invention is applicable to delivery of anesthesia or other fluids to other parts of a living body, either human or animal. In particular, the present invention is applicable to other surgical procedures such as, for example, orthopedic surgical procedures. Thus, although the invention is described in detail with respect to delivery of dental anesthesia, the invention is not intended to be limited to use only in connection with dental procedures.
In general, anesthesia is delivered by injection of a topical anesthetic followed by a deeper injection of anesthetic for desensitizing nerve endings within the region of interest (infiltration) or for blocking off remote sensory nerves which are coupled to the region of interest (nerve blocking).
It is desirable to minimize the amount of anesthesia injected because toxic reactions may result from drug sensitivity or misdirection of the injection needle into the bloodstream. Such risk of toxic reaction is heightened when repeated administration of anesthesia as required, as is often the case with conventional delivery techniques. In addition, conventional administration of dental anesthesia generally results in numbness of the tongue, cheek, lips and/or even part of the face of the patient for some time after a procedure.
As set forth in U.S. Pat. No. 4,944,677 to Alexandre, conventional methods of delivering dental anesthesia include injection into mucous tissue, injection into a ligament, injection into the septum and injection near a nerve-trunk. However, injection into mucous tissue is disadvantageous because it takes a long time for the anesthesia to take effect (about 5 minutes), because the amount of anesthesia is high (about 4 cc), and because adrenalin or another vaso conductor is required for cardiac patients. Injection into a ligament is disadvantageous because it requires high pressure for injection (which causes pain), because injection is into a septic area, because the risk of infection of the ligament is increased, and because the risk of post-operative problems including inflammation and necrosis is increased. Injection into the septum is disadvantageous because it also requires high pressure for injection (which causes pain), because exact positioning of the needle is required, and because injection is into a septic area. And finally, injection near the nerve-trunk is disadvantageous because there is a long delay in effecting anesthesia (about 10 minutes), because there is a high risk of inadvertent injection into a blood vessel, and because post-operative numbness is very long lasting.
Intraosseous delivery of dental anesthesia directly into the jawbone is also known. Intraosseous delivery is extremely advantageous because it very rapidly achieves numbness limited only to the tooth to be treated, because it enables the amount of anesthetic to be significantly reduced, and because post-operative numbness is essentially avoided. The most relevant prior art intraosseous delivery techniques are described hereinbelow.
U.S. Pat. No. 2,317,648 to Siqveland discloses an intraosseous delivery apparatus and method whereby a threaded sleeve is concentrically and removably positioned around a drill. The drill and threaded sleeve are used together to penetrate the bone, and then the drill is detached and withdrawn, leaving the threaded sleeve embedded in the bone as a guide for a hypodermic needle through which anesthesia may be injected. After injection of anesthesia, the threaded sleeve is withdrawn from the bone by reverse rotation. The threaded sleeve disclosed in Siqveland, however, is too expensive to manufacture to be disposable and must be inserted at a slow speed due to the threading. In addition, the drill disclosed in Siqveland is solid, so that debris which is generated by the drill is left in the drilled hole, thereby reducing absorption of the anesthesia into the jawbone.
U.S. Pat. No. 4,944,677 to Alexandre discloses an intraosseous delivery apparatus and method whereby a smooth, hollow drilling needle is used to drill a hole into the jawbone near the apex of a tooth to be anesthetized. The drilling needle is then removed from the jawbone and a hypodermic needle of substantially the same gauge as the drilling needle is then inserted into the hole formed in the jawbone using a single drop of blood formed during drilling as a marker for entrance to the hole. After the hypodermic needle is inserted into the hole, anesthesia is then delivered by injection directly into the jawbone. This technique, however, is disadvantageous because in actual practice it is very difficult to find the drilled hole and insert the hypodermic needle therein.
U.S. Pat. No. 5,432,824 to Akerfeldt et al discloses a method of accessing a hard tissue whereby a needle drill is inserted into and through a cannula and then used to drill a hole in hard tissue. The distal end of the needle drill has eccentrically shaped tip, so that the drilled hole has a larger diameter than the needle drill and the cannula. After the hole is drilled, the cannula is inserted into the oversized hole. The needle drill is then removed, and the cannula is left secured in the bone to act as a guiding channel for sampling or administration of drugs. The needle drill of Akerfeldt et al, however, has a solid drilling tip, so that as in the case of Siqveland, debris which is generated by the drilling tip of the needle drill is left in the drilled hole. Thus, if the method of Akerfeldt et al were used for the injection of anesthesia, the absorption of the anesthesia would be reduced. In addition, drilling of an enlarged hole as taught by Akerfeldt results in more bone removal, a higher degree of heat generation during drilling, more trauma to the patient, a longer healing time, and a higher risk of infection. Still further, because the hole drilled by Akerfeldt is oversized, the cannula is only loosely fitted in the drilled hole, and injected anesthesia may leak backwards out of the hard tissue.
U.S. Pat. No. 5,762,639 to Gibbs discloses an apparatus and method for intraosseously delivering anesthesia whereby a solid rod is inserted into a perforating catheter, and the assembled rod and perforating catheter are used to perforate ligament or bone tissue. After drilling, the rod is removed and the perforating catheter is left in place to be used as a guide for insertion of a hypodermic needle. In Gibbs, the drilling needle is the outside member (i.e., the perforating catheter), and the rod which is inserted into the perforating catheter is used to prevent debris resulting from drilling from blocking the passage in the perforating catheter. The advantage of this technique is that the perforating catheter remains clear for injection of anesthesia, but the disadvantage is that, as in Siqveland and Akerfeldt et al, the debris which is generated by the drilling is left in the drilled hole, thereby reducing absorption of the anesthesia into the jawbone. And because the drilling needle of Gibbs is the outside member and bottoms in the drilled hole, the bottom portion of the drilled hole is large. As in Akerfeldt et al, this results in more bone removal, a higher degree of heat generation during drilling, more trauma to the patient, a longer healing time, and a higher risk of infection.